September weather forecastSunnyvale, TX
September
Weather in September
The first month of the autumn, September, is still a hot month in Sunnyvale, Texas, with an average temperature fluctuating between 69.6°F (20.9°C) and 87.6°F (30.9°C).Temperature
September's onset introduces a mild reduction in the average high-temperature, from a very hot 95.5°F (35.3°C) in August to a tropical 87.6°F (30.9°C). Nighttime temperatures hover around an average low of 69.6°F (20.9°C) in September.Heat index
The heat index for September is appraised at a fiery hot 96.8°F (36°C). Greater safety measures are needed, risk of heat exhaustion and heat cramps is high. Continuous activity might trigger heatstroke.It is essential to grasp that the heat index's numbers are for shade and light wind settings. Heat index values may surge by up to 15 Fahrenheit (8 Celsius) degrees in the presence of direct sunlight.
Note: The heat index, also known as 'feels like' or 'apparent temperature', is an indicator that blends the effects of temperature and humidity to depict perceived warmth. This effect is personal, shaped by the individual's physical activity and heat sensitivity, influenced by factors including wind, clothing, and metabolic variances. Consider that direct sun exposure can intensify the felt heat, adding potentially 15 Fahrenheit (8 Celsius) degrees to the heat index. Heat index values hold great significance to children. Juveniles are regularly less conscious of the need to recuperate and rehydrate. Thirst is a tardy symptom of dehydration - hydration, especially during lengthy physical activities, should be maintained.
The human body cools itself through perspiration, as excessive warmth is removed from the body through sweat evaporation. A surge in relative humidity can disrupt the body's normal cooling function by slowing evaporation, hence reducing the rate at which the body cools and intensifying the perception of heat. Excessive heat gain, when not shed effectively by the body, can result in increasing body temperatures and related hazards.
Humidity
In September, the average relative humidity is 64%.Rainfall
In Sunnyvale, Texas, in September, during 15.3 rainfall days, 2.8" (71mm) of precipitation is typically accumulated. In Sunnyvale, during the entire year, the rain falls for 149.6 days and collects up to 33.35" (847mm) of precipitation.Snowfall
In Sunnyvale, snow does not fall in March through December.Daylight
The average length of the day in September is 12h and 22min.On the first day of the month, sunrise is at 7:01 am and sunset at 7:50 pm. On the last day of September, sunrise is at 7:20 am and sunset at 7:11 pm CDT.
Sunshine
In Sunnyvale, the average sunshine in September is 8.6h.UV index
In September, the average daily maximum UV index is 6. A UV Index of 6 to 7 symbolizes a high health hazard from exposure to the Sun's UV radiation for the average person.Note: In September, the maximum UV index of 6 suggests this advice:
Undertake protective measures and comply with sun safety rules. Shielding against skin and eye damage is essential. Between 10 a.m. and 4 p.m., the Sun's UV radiation is at its peak. Limit your exposure to direct sunlight during these hours. On sunny days, it's ideal to wear sunglasses that filter out UVA and UVB rays.
Published by: Weather U.S. | About Us
Data Sources | Weather Forecasting & Climate
Frequently asked questions
Average temperature in September
Sunnyvale, TX
- Average high temperature in September: 87.6°F
The warmest month (with the highest average high temperature) is August (95.5°F).
The month with the lowest average high temperature is January (54.3°F).
- Average low temperature in September: 69.6°F
The months with the highest average low temperature are July and August (75.7°F).
The coldest month (with the lowest average low temperature) is January (38.8°F).
Average pressure in September
Sunnyvale, TX
- Average pressure in September: 29.97"Hg
The month with the highest atmospheric pressure is January (30.16"Hg).
The month with the lowest atmospheric pressure is June (29.91"Hg).
Average wind speed in September
Sunnyvale, TX
- Average wind speed in September: 6.6mph
The windiest month (with the highest average wind speed) is March (9.8mph).
The calmest month (with the lowest average wind speed) is September (6.6mph).
Average humidity in September
Sunnyvale, TX
- Average humidity in September: 64%
The month with the highest relative humidity is May (75%).
The month with the lowest relative humidity is August (58%).
Average rainfall in September
Sunnyvale, TX
- Average rainfall in September: 2.8"
The wettest month (with the highest rainfall) is October (4.29").
The driest month (with the least rainfall) is February (1.85").
Average rainfall days in September
Sunnyvale, TX
- Average rainfall days in September: 15.3 days
The month with the highest number of rainy days is May (15.4 days).
The month with the least rainy days is January (7.6 days).
Average snowfall in September
Sunnyvale, TX
- Average snowfall in September: 0"
The month with the highest snowfall is February (0.67").
The months with the least snowfall are March, April, May, June, July, August, September, October, November and December (0").
Average snowfall days in September
Sunnyvale, TX
- Average snowfall days in September: 0 days
The month with the highest number of snowfall days is February (1.2 days).
The months with the least snowfall days are April, May, June, July, August, September, October and November (0 days).
Average daylight in September /
Average sunshine in September
Sunnyvale, TX
- Average daylight in September: 12h and 24min
The month with the longest days is June (Average daylight: 14h and 18min).
The month with the shortest days is December (Average daylight: 10h and 0min).
- Average sunshine in September: 8h and 36min
The month with the most sunshine is August (Average sunshine: 11h and 6min).
The month with the least sunshine is December (Average sunshine: 5h and 30min).
Average sunshine days in September
Sunnyvale, TX
- Average sunshine days in September: 13 days
The month with the most sunshine days is January (21.8 days).
The month with the least sunshine days is September (13 days).
Average UV index in September
Sunnyvale, TX
- Average UV index in September: 6
The months with the highest UV index are June, July and August (UV index 7).
The months with the lowest UV index are January and December (UV index 3).
Average cloud cover in September
Sunnyvale, TX
- Average cloud cover in September: 28
The month with the most cloud cover is February (Cloud cover 42).
The month with the least cloud cover is August (Cloud cover 20).
Average visibility in September
Sunnyvale, TX
- Average visibility in September: 6mi
The months with the highest visibility are January, February, March, April, May, June, July, August, September, October, November and December (6mi).
The months with the lowest visibility are January, February, March, April, May, June, July, August, September, October, November and December (6mi).
